Tool joint



Oct. 6, 1942. 1. GARDNER 2,298,049

' 1 Y TOOL JOINT Fil ed m. 26, 1940 INVENTOR ATTORNEYS Patented Oct. 6, 1942 'rooL JoIN'r Robert Irving Gardner, Bakersfield, Calif., sssignor .to Richfield Oil Corporation, Los Angeles, Calif., a corporation of Delaware Application November 26, 1940, Serial No. 367,228

2 Claims. (Cl. 308-4) This invention relates to an improved tool joint of the type generally used to attach oil well drilling tools to the drillpipe. Such tool joints are internally threaded at both ends to receive the drill pipe at one end and the tool shank at the other end, being of larger diameter than the drill pipe, they sustain the brunt of sharp formational wear during the drilling procedure. However, such tool joints are subjected to severe impacts and strains and therefore the usualtool joint steels are chosen, giving due consideration to cost, for toughness and strength rather than on the basis of their ability to resist abrasion. Accordingly, in service, tool joints usually fail from external wear long prior to failure from other causes.

A large part of thecost of keeping drill pipe strings in good condition is due to the necessity for the replacement of worn out'tool joints. As a result many ingenious ways have been devised by manufacturers and tool companies to resleeve worn tool joints for further use. Such proposals have included the application of steel tubular stock and wrapped steel ribbon stock, with welding Wherever necessary. One proposal has involved the provision of Stellite bands welded.

to the outer surface of the tool joint to increase abrasive resistance. However, because of the high cost of the hard facing materials heretofore employed the bands are narrow and therefore tend to crack and chip under the severe impact service, thus wearing away nearly as fast as the rest of the tool joint.

I have devised an improved tool joint having extreme Wear resisting properties. The improved tool joint of my invention comprises a main cylindrical body of steel selected for strength and toughness of the type now generally used in tool joints (for example heat treated S; A. E. 3140-X To this main body there is secured a relatively thick outer wear sleeve of austenitic manganese steel. The manganese content advantageously may approach but should not substantially ex ceed This type of steel, sometimes known asHadfield steel, usually has approximately the following analysis:

Manganese per cent-.. 10-14 Carbon do 1.00-1.40 Silicon do 0.30-1.00 Sulphur do 0.05 maximum Phosphate do 0.10 maximum In the as-cast condition, the structure of this material is martensitic, and the material is hard and brittle. After heat treating by quenching 65 ficiently-thin to permit breaking through with Brinell) tained.

in cold water from 1830F., the structure becomes austenitic and the material has approximately the following physical properties:

Tensil strength lbs./sq. in", 118,000 Proportional limit do 43,000 Elongation-2" per cent 44 Reduction of area do 39 Brinell hardness 190 If, after heat treating as above, the relatively soft steel is heated above 800 F. the original hard brittle martensitic structure will be obtreat to obtain the desired austenitic structure. None of the usual heat treatments, (quenching and drawing, tempering, normalizing, case hardening, etc.) are'applicable tosteel of the above analysis. However, even at atmospheric temperature austenitic manganese steel of this type has the property of work hardening very rapidly. When the material is cold worked, small crystals of martensite appear to separate from the austenite at the grain; boundaries. The recrystallized martensite appears to act like a number of keys between the austenitic grains preventing further slippage.

I have discovered that the conditions under which tool joints operate in service are such that this type'of austenitic manganese steel is of exceptional utility. The use of this type of steel for the entire tool joint is not practical since its propensity for work hardening makes it unsuitedfor fatigue service and, although the material can be ground, machining is too costly. However, if a relatively thick sleeve of austenitic manganese steel is spun-cast or welded to the outer surface of the main body of the tool joint an ideal combination is provided. The outer surface of such a sleeve is subjected in service to suflicient impact, in addition to the wear producing abrasion, to cause theoriginally softmaterial (e. g.. 190 Brinell) to form a thin surface layer which is extremely hard and tough (550-650 The extent of impact in this service is sufiicient always to maintain this even hard outer abrasion resisting layer backed by the I steel.

case is worn away. In this type of abrasion impact service this material will show service of from six to ten times as long as the best alloy Moreover, the hard surface layer is suf- It'then becomes necessary to re-heat fishing slips in order to fasten on to the manganese steel rings with fishing tools.

The accompanying drawing illustrates in quarter-section one form of tool joint embodying my invention. In this tool joint the main cylindrical body of the tool joint I is internally threaded at the lower end with tool joint threads 2 for. attachment to the drilling tool. 7 At its upper end it is internally threaded with pipe threads 3 for attachment to the drill pipe. This main body is advantageously formed from a strong tough steel of the type conventionally employed 'in tool joints, for example a nickelchromium steel such as S. A. E. 3140-X heat treated to give a hardness of 290-310 Brinell. The outer surface of the upper portion of the main body and the inner surface of the sleeve 4 advantageously are finished to give a press fit.

, offsets the slight The austenitic manganese steel sleeve.4 may advantageously be provided with cored holes 5, 6, l and 8 and, when pressed into position, may be additionally secured to the main body by welding at the inner edges of the holes 5-8. Ordinarily considerable difliculty is involved in attempting to weld high manganese steel. However, when '3-5% nickel is added to a plain manganese steel of the composition above described, an alloy is obtained which retains its austenitic structure on normalizing while retaining its other useful properties unchanged. The use of this alloy as a 'welding rod produces welds which areat least 50% as strong as the parent metal. However, it is desirable to severely peen the welds while cooling.

It will be obvious that both the wear sleeves and the tool joint bodies may take many different forms and that various methods of attachment may be employed. Likewise my invention may be incorporated either in new tool joints or in worn tool joints which it is desired to re-sleeve for further use. However, the form illustrated in the drawing is simple, efiective and relatively inexpensive. The increased wear resistance obtained with my improved tool joint more than additional cost involved.

I claim: I

1. Animproved tool joint for rotary well drilling apparatus comprising a main cylindrical bodyportio'n of strong, tough steel of moderate hardness having secured thereto and integral therewith a relatively thick outer wear resisting sleeve of austenitic manganese steel, the composition of which is work hardening whereby an extremely hard and tough abrasion resisting layer is formed thereon in use.

2. An improved tool joint for rotary well drilling apparatus comprising a main cylindrical body portion of strong, tough steel ofmoderate hard ness having secured thereto and integral therewith a relatively thick outer wear resisting sleeve of austenitic manganese steel containing approximately 10 to 14 percent manganese and being capable of work'hardening whereby an extremely hard and tough abrasion resisting layer' is formed thereon in use.

RQBERT IRVING GARDNER. 

